Automated deep fryer

ABSTRACT

An automated deep frying system includes a refrigerated food storage compartment having a portion controller and dispenser, an isolated cooking chamber having a frying vessel and a food basket which is movable to a variety of preselected positions for loading, cooking and dispensing the food, and an air purifier including a smooth cold surface for isolating the by-products of the frying process. The system also includes a microprocessor controller which is programmed for the system operation, including automatic dispensing, preparation and serving of preselected portions of food in response to an operator&#39;s input, as well as energy efficient control of the refrigerated food storage compartment and the air purifier cold plate.

This application is a continuation-in-part of "An Automated VentlessDeep Fryer," Ser. No. 08/190,866, filed Feb. 1, 1994, now U.S. Pat. No.5,367,949.

TECHNICAL FIELD

The present invention relates to a system for automated portioning, deepfrying, and dispensing of food such as french fries.

BACKGROUND ART

Deep fat frying of various foods, including french fries, chicken, fish,onion rings, and breaded vegetables, is a well known and popular methodof cooking. Deep frying equipment utilized by restaurants or otherestablishments for preparing food for public consumption is typicallyexpensive and complex equipment which includes built-in fans, duct work,and filtering systems for venting the airborne by-products of the deepfrying process.

U.S. Pat. No. 5,003,868, issued to Higgins et al., discloses anautomated deep fry vending machine for frying a controllable portion offood in a closed (or ventless) environment. This and other priorattempts at ventless cooking have several drawbacks. The vendingmachines were large and energy inefficient. Also, they were mechanicallycomplex and subject to frequent breakdowns. In addition, existing deepfry machines require frequent service to drain and replace the fryingoil.

It is therefore an object of the present invention to provide a morecompact, self-contained automated deep fryer.

It is another object of the present invention to provide a deep fryerwith improved energy efficiency.

It is another object of the present invention to provide a deep fryerwith an improved air purifier which isolates airborne, bitter smellingorganic compounds in an area remote from the cooking area and the foodstorage area and is easily cleaned and maintained.

It is another object of the present invention to provide a deep fryerwith a sealed cooking chamber which does not allow the airbornebyproducts of the frying process to contaminate the stored food.

DISCLOSURE OF THE INVENTION

In carrying out the above and other objects, the automated deep fryingsystem of the present invention includes a refrigerated food storagecompartment having a portion controller and dispenser, an isolatedcooking chamber having a frying vessel and a food basket which ismovable to a variety of preselected positions for loading, cooking, anddispensing the food, an air purifier including a cold surface forisolating the byproducts of the frying process, and a control forprogrammed dispensing, preparation, and serving of preselected portionsof food in response to an operator's input.

The cooking chamber employs a pivotally mounted access door, upon whichthe food basket is preferably mounted in an orientation which results inpartial immersion of the food basket in the frying vessel when theaccess door is in its closed position, sealing the cooking chamberduring the cooking cycle. The access door is driven by an actuator toone of a plurality of predefined positions, including the aforementionedclosed position for cooking, a partially open position for food loading,a post-cooking, oil-draining position, and a food dispensing position.

The atmosphere of the otherwise sealed cooking chamber is vented to theair purifier which employs a cold plate having a cold surface over whichthe fumes from the cooking compartment travel, and on which water andbitter smelling organic compounds condense. The cold plate is positionedwithin the air purifier chamber in the path of the fumes between theinlet of the air purifier and a filter, through which the air travelsprior to recirculation of the air into the cooking chamber.

The food storage compartment is refrigerated to preserve the food, andincludes a dispensing mechanism including a portion controller fordispensing a pre-selected portion of the food from the storagecompartment into the food basket for deep frying in the cooking chamber.The compartment is preferably cylindrically shaped. The dispensingmechanism preferably comprises a plurality of arms mounted upon a centerpost in the storage compartment such that the arms extend radiallyoutward from the center to the walls of the cylindrical compartment. Thepost is powered for rotation, causing the radial arms to sweep apredetermined arc within the cylinder to collect the food and distributeit efficiently to a portion bin for subsequent release from the foodstorage compartment into the food basket.

The control preferably employs a microprocessor which is suitablyprogrammed to provide the appropriate signals to control the actuatorsfor automatic dispensing, cooking, and serving of the food, as well as avariety of pre-programmed, periodic system maintenance and operationfunctions.

The cooking chamber is also provided with an oil overflow run-off, fromwhich oil from the frying vessel is directed into a remote oil trap. Thecontrol is preferably programmed to periodically add a preselectedamount of oil to the frying vessel to cause the frying vessel tooverflow by a planned amount when the basket containing theto-be-prepared food is immersed in the frying vessel, thereby providingan automatic surface skimming and controlled replenishment of thecooking oil, while maintaining an optimal oil level within the fryingvessel.

These and other objects, features, and advantages of the presentinvention are readily apparent from the following detailed descriptionof the best mode for carrying out the invention, taken in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the fryer of the present invention withthe outer shell shown in phantom;

FIG. 2 is a perspective view of the lower left front portion of thefryer with the access door open;

FIG. 3 is another perspective view of the lower front left corner of thefryer showing the access doors to the food storage compartment andcooking chamber, and including cutaway views of the cooking chamberaccess door drive motor and axle and the frying vessel inside thecooking chamber;

FIG. 4 is a cutaway view of the cooking chamber access door with thefood basket mounted thereon, the frying vessel, and a portion of thefloor of the cooking chamber;

FIG. 5 is a partial cross-sectional side view of the fryer showing thefrying vessel and heating element mounted therein;

FIG. 6 is a partial cross-sectional side view of the fryer showing theaccess doors and food basket in the food load position;

FIG. 7 is a partial cross-sectional side view of the fryer showing thefood basket in the cooking position;

FIG. 8 is a partial cross-sectional side view of the fryer showing thecooking basket in the drain position;

FIG. 9 is a partial cross-sectional side view of the fryer showing thecooking basket in the unload position;

FIG. 10 is a top perspective view of the inside of the food storagecompartment;

FIG. 11 is a partial perspective view of the arms of the portioncontroller;

FIG. 12 is a top view of the food storage compartment;

FIG. 13 is cutaway view of the dispenser arm blade;

FIG. 14 is a perspective view of the lower front right section of thefryer showing the air purifier;

FIG. 15 is a top view in cross-section;

FIG. 16 is a partial cross-sectional view of the filter in the airpurifier;

FIG. 17 is a rear view of the fryer;

FIG. 18 is a schematic view of the rear portion of the fryer showing theair flow therethrough;

FIG. 19 is a block diagram of the controller;

FIG. 20 is a flowchart of the run mode sequence of the refrigerationtask;

FIG. 21 is a flowchart of the idle mode sequence of the refrigerationtask;

FIG. 22 is a partial cross-sectional side view of the fryer showing anembodiment including the oil replenishment system; and

FIG. 23 is a top view of the open food storage compartment showing thefood portion bin and agitator.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, the fryer of the present invention, generallyreferred to as 20, includes a refrigerated food storage compartment 22,an isolated cooking chamber 24, an air purifier 26, and a control 28 forprogrammed dispensing, preparation, and serving of a preselected portionof food in response to an operator's input. All of the components of thefryer 20 are preferably mounted for encasement within a shell 30,preferably made of stainless steel. The shell, of course, includesopenings for access to the food storage compartment, via lid 32, thefood dispensing area via access door 34 (shown in FIG. 2). The shell 30also preferably includes an access door (not shown) which encloses theair purifier 26. The access door enclosing the purifier 26 is preferablypivotally mounted so that it can be moved from its closed position intoan open position to allow access to the purifier 26 for cleaning and/orservice.

Referring now to FIGS. 1-4, the food storage compartment 22 ispreferably mounted above the cooking chamber 24, so that the food can begravity-fed from the storage compartment 22 into the cooking chamber 24.The cooking chamber 24 includes a frying vessel 36 which holds heatedcooking oil, and is of a size and shape adequate to accept a food basket38 containing a preselected portion of the food to be cooked. The volumeof the frying vessel is minimized in order to minimize the amount of oilwhich must be used, as well as to minimize the energy required tomaintain the oil at the proper cooking temperature. In the preferredembodiment, the oil reservoir 35 of the cooking vessel 36 is of agenerally frustoconical shape. The relatively larger volume of oil isthus in the upper portion of the frying vessel 36 which receives thefrying basket 38. The area below the frying basket is significantlyreduced in volume with this frustoconical design, thereby reducing thevolume of oil required and the energy required to heat it, as describedabove.

The outer sidewalls of the frying vessel 36 are generally cylindrical inshape. Any excess oil and surface contaminant which overflow from theoil reservoir will harmlessly flow down the relatively cooler sidewallsof the cooking vessel to the floor of the fryer. The floor is preferablyprovided with a drainage hole through which the excess oil can draininto a suitable container (not shown) for disposal.

It will be appreciated that, by supplying an additional predeterminedamount of new oil to the frying vessel on a periodic basis via, forexample, the injection of the oil from a replenishment reservoir (230,FIG. 22) through suitable conduit (232, FIG. 22), through the wall ofthe cooking chamber 24 into the frying vessel 36, the repeated immersionof the food basket 38 with food into the frying vessel 36 will cause theoil to overflow causing excess oil, including floating debris on thesurface of the oil, to be automatically drained. Thus, by controlledperiodic replenishment of the oil to the frying vessel 36, the variationin oil level between basket in-and-out cycle can be maintained at asignificant enough level to exceed the volume of the frying vessel,thereby insuring periodic drainage of the surface oil and floatingdebris from the fry vessel 36. This automatic surface skimmer eliminatesthe cost and complexity of additional pumps and filters which are oftenused on high-capacity deep frying equipment.

Referring to FIG. 22, in one embodiment of the present invention, an oilreplenishment reservoir 230 is connected, via conduit 232, to the insideof the cooking chamber 24 to supply oil to the oil reservoir 35 of thecooking vessel 36. The control 28 is suitably connected to operate apump 234 based on various preselected criteria to pump a predeterminedamount of oil into the frying vessel reservoir 35. In this embodiment,the optimal amount of oil in the frying vessel reservoir 35 has beenfound to be about 50 ounces. The control increments a cumulative ordercounter upon the preparation of each order. When the cumulative ordercount counter reaches a preselected number of orders, (about 4-16, andpreferably 8), the control generates a signal to activate the pump 234to pump a predetermined amount of oil (about 1-4 ounces, and preferablyabout two ounces) into the reservoir 35 to replenish the oil therein.Upon completion of the replenishment cycle, the control then resets thecumulative order counter to zero to re-start the sequence.

As an alternative to, or supplementing, the automatic oil replenishmentbased upon the number of orders processed, the system may also includelogic for automatic replenishment of oil whenever the oil in the fryingvessel reservoir 35 is detected to be below a predetermined level. Oneembodiment for detecting oil level, shown in FIG. 22, includes a firsttemperature sensor 236 and a second temperature sensor 238 mountedwithin the oil reservoir 35 of the frying vessel 36 and connected asinputs to the controller 28. The first temperature sensor 236 and secondtemperature sensor 238 are commercially available thermistors.

The second temperature sensor 238 is preferably mounted on the inside ofthe frying vessel 36 at a level that is about equal to, or just below,the desired oil level. The first temperature sensor 236 is also mountedwithin the cooking vessel 36 at a relatively deeper location within thereservoir. When the cooking oil is at the normal level, each of thetemperature sensors will indicate approximately the same temperature,the temperature of the oil. If the oil level falls below the level ofthe second temperature sensor 238, it will begin to register asignificantly lower temperature. Thus, by periodically monitoring eachof these temperature sensors, the control can determine when the oillevel within the frying vessel 36 has fallen below a predeterminedacceptable level. In one embodiment, the control logic uses the firsttemperature sensor 236 to determine when the oil is within an acceptableoperating temperature range. If it is, the control then determineswhether the temperature detected by the second temperature sensor 238 islower than the temperature detected from the first temperature sensor236 by more than a predetermined amount. If so, the controller initiatesan oil replenishment cycle as described above. Thus, by counting foodorders processed, or by detecting the level of the oil in the fryingvessel 36, or by some combination of these periodic condition sensingactivities, the system of the present invention can periodicallyautomatically replenish oil in the frying vessel 36, withoutinterruption of normal operation.

In one contemplated embodiment, the logic periodically detects the levelof the oil and, if the level has fallen a predetermined threshold, thecontrol logic generates a signal to the pump to replenish the fryingvessel with enough oil to fill, but not overfill, the frying vessel. Inaddition to this periodic checking and replenishing function, thecontrol logic also activates the pump to pump a selected amount of oil(.preferably about two ounces) when a cumulative order counter reaches apreselected number of orders for the purpose of over-filling the fryingvessel reservoir 35 so that some oil and the floating debris on thesurface of the oil is drained from the frying vessel 36 as describedabove.

Referring to FIG. 5, the frying vessel 36 includes a heating coil 52which is preferably bent into a generally helical configuration, withthe coils having a varying diameter to conform generally with thefrustoconical shape of the oil reservoir, for placement within thefrying vessel immediately below the fully immersed food basket 38. Theheating coil may be of the type generally available such as from theChromalux Company, and includes a conventional plug for removablemounting to an electrical connector on the inside wall of the cookingchamber 24.

It should be noted that, in the embodiment shown in FIG. 22, the oilreservoir 35 in the frying vessel may be configured with a cold space240 below the heating coil 52, thereby allowing food particles and otherby-products to migrate to the bottom of the reservoir 35 where they willbe relatively isolated from the food in the food basket 38. And, sincethe oil in this space will be relatively cooler than the oil in the areaof the reservoir 35 occupied by the heating coil 52, the food particlesand other by-products will react with the oil at a relatively lower ratethan in the hotter oil above the cold spot.

Referring again to FIGS. 3 and 4, the cooking chamber 24 is preferablyisolated from the other components of the fryer, as well as from theoutside environment. The food enters the chamber through an access door54 which is swingably mounted for positioning between a closed position(shown in FIG. 2) sealing off the chamber from the other components inthe external environment, to a plurality of open positions for receivingfood, dispensing food, or maintenance and/or servicing the equipment.The door is preferably mounted on an axle rod 56 which, in turn, ismounted to a drive motor 58 which powers the axle to swing the accessdoor 54 from its closed position to its various preselected openpositions. A second access door 60 is swingably mounted on the undersideof the food storage compartment 22. This access door 60 is preferablyswingable from its closed position to an open position which allows fordischarge of the preselected portion of food into the food basket 38.

FIGS. 6-8 illustrate the various positions of the access doors 54 and 60and the frying vessel 36 during a cooking cycle. Upon receiving theappropriate input (typically upon receiving a signal from a push-button62 (shown in FIG. 1) on the front panel of the fryer 20, the cookingchamber access door 54 is opened to its loading position, and thestorage compartment access door 60 is also opened, thereby releasing thepreselected portion of the food by gravity-feed into the food basket 38.Access door 54 is then moved to its closed position, thereby positioningthe food basket 38 and the food in the frying vessel 36 for cooking foran adjustable, predefined time period. In one embodiment, access door 60is forced to a closed position by its contact with the cooking chamberaccess door 54 during movement of the access door 54 from its loadingposition to its closed position. Once closed, the access door 60 maythen be latched, either mechanically or magnetically. However, as willbe appreciated by those skilled in the art, the food storage compartmentaccess door 60 could be driven by a drive motor in a manner similar toaccess door 54.

At some time following release of the food into the food basket andclosure of the food storage compartment access door, the control 28activates the drive motor in the food storage compartment 22 to delivera predefined portion of the food (as hereinafter more fully described inconjunction with FIGS. 10-13) for discharge from the storage compartment22 during the next cooking cycle.

After the food is cooked for an adjustable, predefined period of time,cooking chamber access door 54 is then automatically positioned from itsclosed position (shown in FIG. 7) to an intermediate draining position(shown in FIG. 8) to allow cooking oil to drain from the ready-to-eatfood back into frying vessel 36. This draining position may be an anglewhich is suitable for simultaneously removing the food from the oil andpositioning the food basket 38 over the frying vessel 36 for drainage ofthe cooking oil into the frying vessel. The draining period is typically4-30 seconds, and preferably about 14 seconds. The draining period isalso preferably of sufficient duration to allow the food surface to coolto the desired eating temperature.

Referring to FIG. 9, the heating chamber access door 54 and the foodbasket 38 are then moved to the discharge position and the food isemptied by gravity-feed into a serving container 63 of suitable size. Itshould be noted that first shield 64 and second shield 66 serve to guidethe falling food into the dish.

The food basket 38 preferably includes a shield 64 which, along with theinside surface of the access door 60, serves as a guideway for thefalling food into the food basket 38.

Referring now to FIGS. 10-13, the food storage compartment 22 includes aportion controller preferably comprising a plurality of radiallyextending arms 70-74 each of which is mounted on a rotating center post76 which in turn is powered by a suitable drive motor. By rotating thecenter post 76, the arms sweep in a circular manner about the entirecircular cross-section of the compartment 22. In the preferredembodiment, one or more of the arms 72 and 74 are mounted at a suitabledistance above the floor 78 of the storage compartment to help move,without damaging, the food pieces as the center post and arms arerotated within the compartment 22. One arm 70 is provided with a barrier80 which, upon rotation of the portion control aggregates and sweeps thefood ahead of it as the arm is rotating.

A portion bin 82 is located immediately below the floor 78 of the foodstorage compartment 22. The portion bin 82 is loaded with food via anopening 84 in the floor of the food storage compartment 22 by rotationof the portion dispenser for a suitable number of revolutions. In thepreferred embodiment, it has been found that by locating dispensing arm70 with barrier 80 just past the opening 84 and rotating the center post76 in a counterclockwise direction until it again sweeps past theopening 84, enough food is swept through the opening 84 into the portionbin 82 for subsequent release for cooking. In one embodiment, thecontroller includes an adjustable, predefined "portion remainingcounter" which is decremented as each portion is dispatched for cooking.When the amount of food is above a predefined threshold, the controlarms sweep through a 360° arc to direct a full portion of food into thefood compartment, leaving them in the orientation shown in FIG. 11. Whenthe counter is reduced to a predefined value, the arms 70-74 are sweptthrough a multiple number of complete revolutions (preferably threerevolutions), to ensure that the appropriate volume of food is orientedand swept into the portion bin 82 from the now-reduced volume of foodcontained in the food storage compartment 22. When the portion remainingcounter is decremented to an adjustable, predefined count, the controlmay transmit a signal to, for example, power a light or buzzerindicating to the operator that the food storage compartment 22 needs tobe refilled.

In an alternative embodiment, weight sensing means may be located in thefood storage compartment 22 to sense the weight of, and therebydetermine the amount of, food in the compartment.

In another alternative embodiment, additional weight sensing means maybe located in the portion bin 82 and coupled to the control in order toportion the food by weight rather than volume. In this alternativeembodiment, the control would transmit a signal to the drive motor ofthe portion dispensing arms to stop rotation of the arms once the weightsensor in the portion bin registered the predetermined portion weight.

In another alternative embodiment which is particularly suitable forautomatically dispensing frozen food by count, rather than by weight orvolume, a conventional electric eye may be positioned in the path of theopening 84 to sense when food has fallen through the opening into theportion bin 82 and maintain a count thereof. In this embodiment, theopening would be configured in a size suitable to allow one piece offood (e.g., one chicken nugget) through the opening at a time. If thepreselected portion count for the food items is, for example, six, thesystem control could stop movement of the control arms when the countsensed by the electric eye reaches six. This embodiment may also includea movable barrier which may be actuated to cover the opening 84 once thenumber of food items equal to the portion count has passed through theopening.

As shown in FIG. 12, the control arms 70-74 are preferably mounted uponthe center post 76 such that the arms extend on a tangent from the outersurface of the center post outward to the wall of the storagecompartment 22. When mounted in this manner, the food is urged, uponrotation of the arms 70-74, from the center of the food compartmenttowards the outer wall of the compartment where the opening 84 for theportion bin 82 is located.

Referring to FIG. 13, the end of the barrier 80 preferably comprises aplurality of plastic strips 86 which, in contrast to the solid plasticportion of the barrier 80 are more forgiving as they brush the foodpieces up to and over the opening 84 into the food bin. This structurereduces the likelihood of breakage of the frozen food pieces as they aredispensed into the portion bin.

Referring again to FIGS. 22 and 23, an agitator 242 may be provided onthe inside of the access door 60 of the food storage compartment tointerfere with the food collected in the portion bin when the accessdoor 60 is open to deliver the food portion to the food basket 38. Theagitator 242 may be an elongate post mounted in the generally verticalorientation on the inside of the access door 60, such that as the accessdoor drops open, the post moves through the portion bin, therebyjostling the food therein to ensure that it has not frozen in placewithin the portion bin. It should also be noted that the access door 60may be spring loaded so that the spring force assists the opening of thedoor when desired. It will be appreciated that the agitator 242, as wellas a spring mount on the access door 60, serve to prevent the food andthe door, respectively, from freezing in place in the event there is along duration of time between orders.

Referring now to FIGS. 14 and 15, the air purifier 26 includes acondenser in the form of a generally smooth planar cold plate 90interposed in the purifier chamber between air inlets 92-94 and fan 96.Fumes from the cooking chamber 24 are drawn through suitable conduits98-100, through inlets 92-94. The fumes are entrained along the majorsurfaces of the cold plate 90 where much of the water and volatileorganic compounds are condensed out of the atmosphere where they trickledown the plate to a drain (not shown) in the floor 102 of the purifierchamber. The drain opening in the floor 102 can be connected directly toa permanent drain, or can be fitted to a temporary removable holdingtank 104 such as that shown in FIG. 14. The entrained fumes flow up theopposite major surface of the cold plate and around barrier 106 wherethey are drawn through an additional filter 108. Filter 108 can be aconventional charcoal filter, or it can be a filter box 110 (shown inFIG. 16) including a screen 112 upon which charcoal granules 114 areplaced and through which the entrained fumes travel as they are drawn bythe fan 96 through the outlet 116, through a second conduit 118, andback into the cooking chamber 24. Thus, the cold plate condenses outbitter smelling organic compounds and the filtered fumes are returned tothe remote cooking chamber 24, thereby keeping the atmosphere of thecooking chamber smelling fresh.

In an alternative embodiment, the entrained fumes may be vented out ofthe fryer, and preferably out of the building in which the fryer isinstalled, rather than recycled through the second conduit 118 back intothe cooking chamber 24.

It will be appreciated by those skilled in the art that the simpledesign of the air purifier allows for easy cleaning by wiping off thesmooth-surfaced, solid cold plate and replacing the charcoal filter.This easy-to-clean and maintain purifier is a stark contrast to previousconventional filtering systems with more complex conventional filterswhich are harder to maintain and must be frequently replaced. Also, useof a cold plate containing suitable liquid, such as water, increases theenergy efficiency of the purification system, since, once the cold platecontents are chilled, or at least partially frozen, minimalrefrigeration is required to maintain the cold plate in its optimaloperating condition.

As further described hereinafter, the location of the conduits 98, 100from the outlet of the cooking chamber 24 to the inlet of the airpurification chamber 26 efficiently utilizes the heat exchange of thecooling air drawn through the back of the unit and over the surface ofthe conduits, thereby aiding in the cooling of the fumes for latercondensation of unwanted volatiles in the purifier, and furtherincreasing the energy efficiency of the unit.

Referring now to FIG. 17, the fryer 20 of the present inventionpreferably utilizes a single compressor 120, condenser 122, and fan 124to refrigerate both the food storage compartment 22 and the cold plate90. The control 28 is operably connected to valves 126 and 128 to routeliquid refrigerant either to the food storage compartment 22 throughconduit 130, or to the cold plate via conduits 132, as required. Aconventional filter 134 is utilized in the preferred embodiment toremove excess water from the refrigerant as it is cycled from therefrigeration condensing unit 122 back through the cooling system. Sincethe amount of refrigerant required to effectively cool the food storagecompartment 22 is less than that required to maintain the cold plate 90,a reservoir 136 is utilized to collect refrigerant upstream from thevalve 126 and to dispense that refrigerant when the valve 126 is openedto circulate the refrigerant through conduits 132 to the cooling plate,In this manner, adequate refrigerant is quickly routed to the coolingplate when the central control 28 terminates the food storagecompartment 22 cooling cycle and initiates the cooling plate coolingcycle. The refrigeration condensing unit may comprise any condenser andcompressor combination adequate to cool the refrigerant. A Blissfield#60033 condenser is preferably utilized as the condenser, and a TecumsehAE3425Y compressor is preferably utilized as the compressor for thefryer 20 of the present invention. While these components are adequateto service both the food storage compartment 22 in the cold plate 90,other known cooling systems may be employed to separately maintain thefood storage compartment 22 and the cooling plate 90 at operationaltemperatures. However, the use of the single refrigeration systemcoupled with the central control 28 to cool both the food storagecompartment 22 and the cold plate 90 results in a less complex, lowercost system with reduced peak power demand.

While the fryer 20 is normally covered with a stainless steel shell 30,the system is more than adequately ventilated by the fan 24 which drawsambient air through a screened opening 138 in the base 140. It should benoted that this air flow through the back of the fryer 20 is engineeredto maximize the energy efficiency of the system. Referring to FIG. 18,as the relatively cool ambient air is drawn in through the screened vent138, it travels past the compressor 120 by the conduits 98, 100, and thecondenser 122, and is drawn by the fan 124 past the other end of theconduits 98, 100 and out the top. One or more baffles, such as thebaffle 142, may be employed to confine the relatively cooler air on oneside of the unit where it absorbs the heat of the compressor and theconduits 98, 100 containing the hot vapor being routed from the cookingchamber 24 to the purifier 26. As the ambient air travels past thecondenser and through the fan 124, it has picked up heat through thepreviously described heat exchange. However, it is still capable ofabsorbing some heat from the other side of the conduits 98, 100, sincethe fumes traveling through the conduits (at 144) are relatively hotterat the exit point of the cooking chamber 24 than at the points (at 146)where the fumes are about to enter the purifier 26 for further coolingand condensation. Thus, the ambient air intake and flow is directed toachieve maximum heat exchange, thereby further increasing the energyefficiency of the system.

Referring now to FIGS. 1 and 19, the fryer 20 preferably utilizes aprogrammable control 28 which operates the aforementioned refrigerationsystem to maintain the appropriate temperatures in the food storagecompartment 22 and the cold plate 90, operates the heating coil whenrequired to maintain the appropriate cooking temperature in the fryvessel 36, and powers the appropriate drive motors to generate the foodportioning, dispensing, cooking, draining, and delivery cycles inresponse to an operator input.

In the preferred embodiment, the control includes a conventionalmicroprocessor with a multi-task operating system, such as the MotorolaM6802, with the suitable system maintenance and operation cyclesprogrammed and permanently encoded in a read-only memory (ROM) chip,such as Intel #2764. The microprocessor includes a suitable number ofinputs to allow for connection to various system condition sensors,including temperature and/or weight sensors for providing temperatureand/or weight data from the food storage compartment 22, cooking chamber24 and cold plate 90, as well as other inputs which are connected tomanual operator switches 62, 148 and/or control panel lights (notshown).

Referring to FIG. 19, the basic tasks performed by the controllerinclude the clock task, the basket cycle control task, the oiltemperature control task, and the refrigeration control task. The clocktask, indicated at 202, includes periodically (preferably every second)monitoring system inputs, including any operator switches and/orpush-buttons to determine whether any switches and/or push-buttons havebeen activated. Upon determining that a switch or push-button, or anyother monitored input, has been activated, the clock task then signalsthe controller to perform whatever other appropriate tasks are requiredin response to the activated input. The clock task may also outputsignals, as appropriate, necessary to activate any status indicatorlamps or horns.

When, for example, the clock task determines that the operator hasactivated the appropriate switch to begin a cooking cycle, thecontroller, at 204, transmits the output signals necessary to complete acooking cycle. For example, in one embodiment, a signal activating themotor to drive the access door and food basket to its loading position,as previously described, is transmitted by the control task logic alongwith the necessary signal to release the food storage compartment doorlatch, thereby releasing the food from the portion bin into the waitingfood basket. The access door motor is then powered to close the door,and immerse the basket in the frying vessel. At a predetermined timethereafter (preferably within a few seconds after the food storagecompartment door is closed), the drive motor for the portion controlleris activated as previously described to deposit another portion of foodin the portion bin for the next cooking cycle.

After a predetermined time and/or oil temperature conditions (about30-150 seconds and preferably about 40 seconds), the basket cyclecontrol then activates the access door drive motor as required toposition the access door and food basket to the drain position. Uponlapse of the pre-set draining time (about 4-30 seconds and preferably 14seconds), the control 28 again activates the drive motor for the accessdoor 54 to position the door in the discharge position (shown in FIG.9), thereby delivering the ready-to-eat food to a suitable container 62.After another predetermined time period, the control signals the accessdoor motor as appropriate to drive the motor to position the access doorand the now empty food basket in the closed position, completing thecooking cycle and placing the system in the ready position for the nextcooking cycle. The time periods for each of the sections of the cyclemay, of course, be varied, depending upon the size of the fryer 20, thetype of food, the size of the portion, etc.

It will be appreciated that, as described above, many of the steps ofthe cycle initiated on a timed basis, these steps could alternatively beinvoked as a result of other inputs (e.g., position sensors, weightsensors, etc.) without departing from the spirit of the invention.

Referring still to FIG. 19, the controller also simultaneously performsthe oil temperature control tasks indicated at 206 necessary to powerthe heating coil to heat the oil at start-up, during a cooking cycle,and when the system is ready but idle. The oil temperature control taskmonitors inputs such as an oil temperature thermistor (which ispreferably mounted in the oil reservoir below the immersed food basket.Again, however, one or more suitable time-based temperature maintenancecycles, based upon pre-set time periods, may be employed in place of orto augment the temperature-responsive control described herein.

At start-up, the oil temperature control task drives the heating coil atfull power (about 1300 watts) to provide a rapid ramp-up of the oiltemperature in preparation for operation of the system.

During idle times, the control powers the heating coil at a reducedpower (about 400 watts) to save energy, and to reduce burning of thecooking oil during idle periods. The control can continuously monitorthe input of the oil temperature thermistor to determine whether the oiltemperature has fallen below a predetermined lower threshold of thecooking temperature range. In one embodiment, the control automaticallysignals the heating coil to operate at full power at the onset of acooking cycle in anticipation of the temperature drop resulting from theimmersion of the frozen food in the oil during cooking. However, the oiltemperature control task could alternatively power the heating coil tocontrol the temperature of the oil solely as a function of the inputfrom the oil temperature thermistor.

The control may also include logic to power the heating coil on a dutycycle whenever the system is ready but idle. For example, in oneembodiment, the control generates signals to power the heating coil atfull power for a period of 200 milliseconds, followed by power off for300 milliseconds, full power for 200 milliseconds, and so on. This dutycycle operation of the heating element lowers the heating element's skintemperature by about 50 degrees, which reduces the rate of degradationof the oil, as well as reducing the power consumption of the heatercoil.

The control may also be provided with logic for determining cooking oilage so that the system is automatically disabled from use whenever thecooking oil has been at an operating temperature for a period of time inexcess of a predetermined value. If the oil has been "hot," i.e., abovethe predetermined value, for a period greater than the selected time,the control transmits a signal to disable the power to the heating coiland/or inhibits the operation of the basket cycle control task, tothereby prevent operation of the deep fryer until the oil has beenreplaced with new oil. The control may also signal a warning light orbuzzer (not shown) to indicate to the operator that the system is lockedout due to the age of the oil. In one embodiment, a cumulated operatingtime of 120 hours is the threshold beyond which the control disablesoperation of the heater coil and/or food basket and indicates an "oldoil" condition. It will be appreciated that the control may signal awarning light or buzzer indicating oil age at the same time as itdisables the heater coil or food basket or, alternatively, at apreselected earlier time to give the operator advance warning of theneed to change the oil prior to shut down.

In the refrigeration cycle, the control, at 208, alternates circulationof refrigerant between the freezer in the food storage compartment 22and cold plate 90 in the air purifier 26. The flowchart for the run modesequence employed by the refrigeration control task 208 is illustratedin FIG. 20. When the controller begins performance of the refrigerationcontrol task at 212 during the normal operating mode of the fryer, thecontrol transmits the appropriate signals, at 214, to activate thevalves necessary to route the refrigerant to the cold plate 90 untileither the cold plate thermistor indicates that the cold platetemperature has dropped below a predefined set point, or until somepredefined maximum cycle time has elapsed. The system next checks thefood storage compartment temperature at 216. If the food Storagecompartment temperature is above the predefined set point, the systemactivates the appropriate valves to circulate the refrigerant to thefood storage compartment for a predefined period, again, preferably fiveminutes. If the food storage compartment is below the predefined setpoint, the system, at 218, stops the compressor for a predeterminedperiod, opens the valve to the plate coil and after delaying (about 3minutes) for pressure equalizations, restarts the compressor, asindicated at 220. It should be noted that the control preferablyautomatically suppresses any signals by the oil temperature control taskto power the heater coil during compressor start-up to minimize the peakpower load of the system. Thus, by limiting the refrigeration cycle foreither the freezer or the cold plate to a maximum time, preferably aboutfive minutes, (or less, if the food storage compartment freezer or coldplate has reached a suitable temperature), the refrigeration controleffectively maintains both the cooling plate 90 and the food storagecompartment 22 at their operating temperatures, both at run time andwhile the fryer is idle, without the need of redundant space-consumingand energy-consuming refrigeration systems.

FIG. 21 illustrates the idle mode sequence utilized by the refrigerationcontrol task 208. When the fryer is in idle mode, such as when it isturned off after food service hours or otherwise for prolonged periods,a simpler sequence is invoked by the refrigeration control task whichdevotes compressor time and the energy related thereto solely tomaintaining the appropriate temperature in the food storage compartment.During idle mode, the refrigeration control task operates theappropriate valves to route refrigerant to the food storage compartmentand, as required, operates the compressor to refrigerate the foodstorage compartment until it falls below a predetermined set point. Therefrigeration control task next shuts down the compressor for apredetermined rest period, preferably ten minutes, as indicated at 226,and equalizes the differential pressure through the cold plate coil.Following the lapse of the predetermined rest period, the compressor isrestarted, at 228, completing the idle mode refrigeration cycle.

The control 28 is preferably programmed to detect multiple inputs (e.g.an operator pressing the push-button 62 three times), storing the numberof inputs, and repeating the cooking cycle accordingly for preparationof multiple portions.

While the best mode for carrying out the invention has been described indetail, those familiar with the art to which this invention relates willrecognize various alternative designs and embodiments for practicing theinvention as disclosed by the following claims.

What is claimed is:
 1. An automated deep fryer comprising:a refrigeratedfood storage compartment connected with a portion controller and fooddispenser; a cooking chamber isolated from the storage compartment, thecooking chamber including a food basket mounted for movement to avariety of preselected positions; a control for programmed dispensing,preparation and serving of a preselected portion of food in response toan operator's input; and an air purifier connected with the cookingchamber, said air purifier including a fan for extracting gases from thecooking chamber, and a cold plate having a generally smooth surface overwhich the fumes from the cooking chamber travel, the cold plate beinginterposed between the fan and the cooking chamber.
 2. The deep fryer ofclaim 1 further including means for recirculating the purified air intothe cooking chamber.
 3. The deep fryer of claim 1 wherein the airpurifier further includes a filter positioned between the cold plate andthe fan.
 4. The deep fryer of claim 1 further including a vent connectedto the air purifier and through which gases are removed from the deepfryer.
 5. An automated deep fryer comprising:a cooking chamber includinga frying vessel having an oil reservoir, an access door, and a foodbasket mounted for controlled movement to a variety of preselectedpositions including a closed position with the food basket at leastpartially immersed in the frying vessel; a refrigerated food storagecompartment including a portion controller and food dispenser, and asecond access door mounted on the storage compartment for controlledmovement from a closed position to an open position through which foodmay be dispensed into the food basket; and a control for the dispensing,preparation and serving of a preselected portion of food in response toan operator's input.
 6. The deep fryer of claim 5 further including anair purifier connected with the cooking chamber, said air purifierincluding a fan for extracting the gases from the cooking chamber , anda condenser for removing water and other by-products from the gases. 7.The deep fryer of claim 6 including means for recirculating the purifiedair into the cooking chamber.
 8. An automated deep fryer comprising:acooking chamber including a frying vessel having an oil reservoir, and afood basket mounted for controlled movement to a variety of preselectedpositions; a refrigerated food storage compartment including a portioncontroller and food dispenser; an air purifier connected with thecooking chamber, said air purifier including a fan for extracting gasesfrom the cooking chamber and a condenser for removing water and otherby-products from the gases; and a control including a processor having aplurality of inputs connected to sensors in the cooking chamber and foodstorage compartment, a plurality of outputs connected to the cookingchamber and food storage compartment, and associated logic forautomatically controlling the operation of the fryer to maintain theappropriate temperatures in the food storage compartment, the purifiercondenser, and the cooking vessel, as well as dispense, prepare andserve a preselected portion of food in response to an operator's input.9. The deep fryer of claims 1 or 8 wherein the cooking chamber furtherincludes an access door mounted for controlled movement to a variety ofpreselected positions, and wherein the food storage compartment includesa second access door mounted for controlled movement from a closedposition to an open position through which food may be dispensed intothe food basket.
 10. The deep fryer of claim 9 wherein the food basketis mounted on the access door.
 11. The deep fryer of claims 6 or 8wherein the condenser comprises a cold plate interposed between the fanand the cooking chamber, the cold plate having a generally smoothsurface over which the fumes from the cooking chamber travel.
 12. Thedeep fryer of claim 11 wherein the cold plate is filled with a liquidwhich is suitably chilled to maintain the surface of the cold plate atthe desired operating temperature.
 13. The deep fryer of claim 12wherein the liquid is at least partially frozen to maintain the surfaceof the cold plate at the desired operating temperature.
 14. The deepfryer of claims 5 or 8 further including a vent through which gases areremoved from the deep fryer.
 15. The deep fryer of claim 9 wherein thefood storage compartment is located generally above the cooking chamberand the second access door is mounted on the bottom wall of the storagecompartment for dispensing food with the aid of gravity.
 16. The deepfryer of claim 9 wherein the second access door is located outside thecooking chamber whereby the cooking chamber is isolated from the storagecompartment when the access door on the cooking chamber is closed. 17.The deep fryer of claim 16 wherein the cooking chamber access door ismounted on a generally vertical side wall of the cooking chamber, andwherein the second access door is mounted in a spaced relationship tothe cooking chamber access door such that when the access door and thesecond access door are each moved to the load position the food isreleased from the storage compartment directly into the food basket. 18.The deep fryer of claim 17 wherein the cooking chamber access door ispositioned on the side wall of the cooking chamber such that, as thecooking chamber access door is moved to a closed position, the topsurface of the cooking chamber access door contacts the second accessdoor and urges the second access door into a closed position, andwherein when the cooking chamber access door reaches the closedposition, the top surface of the cooking chamber access door contactsthe second access door and maintains the second access door in theclosed position.
 19. The deep fryer of claims 1, 5 or 8 wherein thestorage compartment is generally circular in cross section, and whereinthe portion controller and dispenser comprises a plurality of radiallyextending arms each of which is mounted on a rotating center postpowered by a drive motor, and wherein at least one arm is provided witha barrier which, upon rotation of the portion controller, aggregates andsweeps the food ahead of it as the arm is rotating, and a portion binlocated immediately below the floor of the storage compartment.
 20. Thedeep fryer of claim 19 wherein the control includes logic fortransmitting a signal to activate the drive motor in the portioncontroller and dispenser to rotate the center post by an amount suitableto load the portion bin with a preselected portion for subsequentrelease into the food basket.
 21. The deep fryer of claim 20 wherein theportion controller and dispenser further includes an adjustable,pre-defined portion remaining counter which is decremented as eachportion is dispatched, and wherein the signal transmitted by the controlto the portion controller and dispenser drive motor varies the extent ofrotation of the center post as a function of the then current value ofthe portion remaining counter.
 22. The deep fryer of claim 19 whereinthe portion controller and dispenser further includes an adjustable,pre-defined portion remaining counter which is decremented as eachportion is dispatched, and the control further includes logic fortransmitting a signal to power an indicator to the operator that thefood storage compartment needs to be refilled whenever the portionremaining counter is decremented to a predefined value.
 23. The deepfryer of claim 19 wherein the portion bin further includes a weightsensor for sensing the weight of the food in the portion bin, andwherein the control is connected to the weight sensor and includes logicto vary the signal transmitted to the portion controller and dispenserdrive motor as a function of the output of the weight sensor to therebydirect the appropriate weighted portion into the portion bin.
 24. Thedeep fryer of claim 19 wherein the food storage compartment includes aweight sensor, and wherein the control is connected to the weight sensorfor periodic receipt of signals therefrom to thereby determine theamount of food remaining in the storage compartment.
 25. The deep fryerof claim 19 wherein the control arms are mounted upon the center postsuch that the arms extend generally tangentially from the outer surfaceof the center post outward to the wall of the storage compartment. 26.The deep fryer of claim 19 wherein the barrier comprises a plurality ofplastic strips.
 27. The deep fryer of claims 5 or 8 wherein the oilreservoir has a generally tapered cross section, thereby reducing thevolume of the oil in the reservoir beneath the food basket.
 28. The deepfryer of claims 5 or 8 wherein the oil reservoir is generallyfrustoconically shaped.
 29. The deep fryer of claims 5 or 8 wherein theouter side walls of the frying vessel are generally cylindrical inshape.
 30. The deep fryer of claims 5 or 8 further including a heatingcoil having a generally helical configuration with the coils having avarying diameter to conform generally with the shape of the oilreservoir, the heating coil being removably mounted within the fryingvessel such that the coil extends into the oil reservoir in the spaceimmediately below the space occupied by the fully immersed food basket.31. The deep fryer of claim 30 wherein the frying vessel furtherincludes a cold space below the space in the frying vessel occupied bythe heating coil.
 32. The deep fryer of claim 9 further including anagitator mounted on the inside surface of the second access door, whichagitator contacts the food in the portion bin as the second access doormoves from the closed to the load position, thereby jostling the frozenfood portion to ensure that it falls from the portion bin into the foodbasket.
 33. The deep fryer of claim 32 wherein the agitator is anelongate post mounted on the inside surface of the second access door toextend generally vertically within the portion bin when the secondaccess door is in the closed position and sweep through the area of theportion bin containing the food as the second access door moves from theclosed position to an open position for unloading the food into the foodbasket.
 34. The deep fryer of claims 5 or 8 wherein the control furtherincludes logic for monitoring the cumulative operating time that the oilin the oil reservoir has been maintained at a preselected operatingtemperature, comparing the cumulative operating time to a preselectedoil age threshold time, and, when the cumulative operating time exceedsthe oil age threshold time, generating signals which inhibit the deepfryer from heating the oil.
 35. The deep fryer of claims 5 or 8 whereinthe control further includes logic for monitoring the cumulativeoperating time that the oil in the oil reservoir has been maintained ata preselected operating temperature, comparing the cumulative operatingtime to a preselected oil age threshold time, and, when the cumulativeoperating time exceeds the oil age threshold time, generating signalswhich disable the deep fryer from any food dispensing or preparationoperations.
 36. The deep fryer of claim 8 wherein the logic formaintaining the appropriate temperatures in the food storage compartmentand the purifier condenser performs a refrigeration control task whichgenerates control signals to alternate the circulation of refrigerantbetween the freezer in the food storage compartment and the purifiercondenser to simultaneously and efficiently maintain both the foodstorage compartment and the purifier condenser at operatingtemperatures.
 37. The deep fryer of claim 34 further including a heatingelement removably mounted within the frying vessel such that the elementextends into the oil reservoir in the space below the space occupied bythe fully immersed food basket, wherein the logic for maintaining theappropriate temperature in the cooking vessel performs an oiltemperature control task which generates control signals to power theheating element at system start-up, during a cooking cycle, and when thesystem is ready but idle.
 38. The deep fryer of claim 37 furtherincluding a refrigeration condensing unit for cooling the refrigerantcirculated to the freezer in the food storage compartment and the coldplate in the air purifier and wherein the logic for automaticallycontrolling the operation of the fryer to maintain the appropriatetemperatures in the food storage compartment, the purifier condenser,and the cooking vessel includes logic for suppressing any signalsotherwise generated by the oil temperature control task logic to powerthe heater coil whenever the refrigeration control task logic hasgenerated signals to start the compressor, thereby minimizing the peakpower load of the system.
 39. The deep fryer of claim 37 wherein the oiltemperature control task logic includes logic for generating controlsignals to power the heating element on a time-based duty cycle when thesystem is ready but idle.
 40. The deep fryer of claim 39 wherein thetime-based duty cycle consists of alternating between maintaining theheating element on for about 200 milliseconds and off for about 300milliseconds during the period when the system is ready but idle,thereby reducing the skin temperature of the element and reducingdegradation of the cooking oil.
 41. The deep fryer of claims 5 or 8further including an oil replenishment reservoir;an oil conduitconnected at one end to the oil replenishment reservoir and having theopposite end discharging into the frying vessel reservoir; a pumpconnected to a conduit for controlled discharge of the oil from the oilreplenishment vessel into the frying vessel; and wherein the controlincludes logic for periodically activating the pump to discharge oilinto the frying vessel based upon the existence of preselectedconditions.
 42. The automated deep fryer of claim 41 wherein the logicincludes an order counter for counting the number of food ordersprepared by the deep fryer, logic for activating the pump to discharge apreselected amount of oil into the frying vessel after the order counterhas reached a predetermined value, and setting the order counter to zeroupon discharge of the preselected amount of oil.
 43. The deep fryer ofclaim 41 further including:first sensing means mounted within the fryingvessel generally at a depth equal to the location of the bottom of thefully immersed food basket; a second temperature sensing means locatedin the frying vessel at a depth just below the desired oil level; andwherein the control includes logic for periodically monitoring thesignals received from the first and second temperature sensors, andgenerating a signal to activate the pump to discharge oil into thefrying vessel whenever the signals from the first and second temperaturesensors meet preselected criteria.
 44. The deep fryer of claim 43wherein the preselected oil replenishment criteria is that the firsttemperature sensor indicates a temperature greater than a firstpreselected value and the second temperature sensor indicates atemperature less than a second preselected value.
 45. The deep fryer ofclaim 19 wherein the portion bin further includes a sensor for sensingthe number of food items which have fallen into the portion bin, andlogic for comparing the number sensed to a preselected portion countand, when the sensed number of items in the portion bin is equal to thepreselected portion count, generating a signal to the portion controllerand dispenser to stop dispensing items into the portion bin, therebydispensing the food items by count.
 46. The deep fryer of claim 1wherein the cold plate is filled with a liquid which is suitably chilledto maintain the surface of the cold plate at the desired operatingtemperature.
 47. The deep fryer of claim 46 wherein the liquid is atleast partially frozen to maintain the surface of the cold plate at thedesired operating temperature.
 48. The deep fryer of claim 5 wherein thefood storage compartment is located generally above the cooking chamberand the second access door is mounted on the bottom wall of the storagecompartment for dispensing food with the aid of gravity.
 49. The deepfryer of claim 5 wherein the second access door is located outside thecooking chamber whereby the cooking chamber is isolated from the storagecompartment when the access door on the cooking chamber is closed. 50.The deep fryer of claim 49 wherein the cooking chamber access door ismounted on a generally vertical side wall of the cooking chamber, andwherein the second access door is mounted in a spaced relationship tothe cooking chamber access door such that when the access door and thesecond access door are each moved to the load position the food isreleased from the storage compartment directly into the food basket. 51.The deep fryer of claim 50 wherein the cooking chamber access door ispositioned on the side wall of the cooking chamber such that, as thecooking chamber access door is moved to a closed position, the topsurface of the cooking chamber access door contacts the second accessdoor and urges the second access door into a closed position, andwherein when the cooking chamber access door reaches the closedposition, the top surface of the cooking chamber access door contactsthe second access door and maintains the second access door in theclosed position.
 52. The deep fryer of claim 5 further including anagitator mounted on the inside surface of the second access door, whichagitator contacts the food in the portion bin as the second access doormoves from the closed to the load position, thereby jostling the frozenfood portion to ensure that it falls from the portion bin into the foodbasket.
 53. The deep fryer of claim 8 further including a heatingelement removably mounted within the frying vessel such that the elementextends into the oil reservoir in the space below the space occupied bythe fully immersed food basket, wherein the logic for maintaining theappropriate temperature in the cooking vessel performs an oiltemperature control task which generates control signals to power theheating element at system start-up, during a cooking cycle, and when thesystem is ready but idle.
 54. The deep fryer of claim 53 furtherincluding a refrigeration condensing unit for cooling the refrigerantcirculated to the freezer in the food storage compartment and the coldplate in the air purifier and wherein the logic for automaticallycontrolling the operation of the fryer to maintain the appropriatetemperatures in the food storage compartment, the purifier condenser,and the cooking vessel includes logic for suppressing any signalsotherwise generated by the oil temperature control task logic to powerthe heating element whenever the refrigeration control task logic hasgenerated signals to start the compressor, thereby minimizing the peakpower load of the system.
 55. The deep fryer of claim 53 wherein the oiltemperature control task logic includes logic for generating controlsignals to power the heating element on a time-based duty cycle when thesystem is ready but idle.
 56. The deep fryer of claim 55 wherein thetime-based duty cycle consists of alternating between maintaining theheating element on for about 200 milliseconds and off for about 300milliseconds during the period when the system is ready but idle,thereby reducing the skin temperature of the element and reducingdegradation of the cooking oil.